1. Technical Field
The present invention pertains to improvements in methods and apparatus for producing and collecting sterile slush. In particular, the invention is an improvement in the methods and apparatus disclosed in U.S. Pat. Nos. 4,393,659 (Keyes et al), U.S. Pat. No. 4,934,152 (Templeton), U.S. Pat. No. 5,163,299 (Faries, Jr. et al), U.S. Pat. No. 5,331,820 (Faries, Jr. et al), U.S. Pat. No. 5,400,616 (Faries, Jr. et al), U.S. Pat. No. 5,502,980 (Faries, Jr. et al) and the patents cited therein. The disclosures in the aforementioned patents are expressly incorporated by reference herein in their entireties. In addition, the present invention relates to subject matter disclosed in copending U.S. patent application Ser. No. 08/810,104 filed Feb. 25, 1997, entitled "Surgical Drape for Use with Surgical Slush Machines Having an Automatic Dislodgement Mechanism".
2. Discussion of Prior Art
The above-referenced Keyes et al patent discloses a surgical slush producing system having a cabinet with a heat transfer basin at its top surface. A refrigeration mechanism in the cabinet takes the form of a closed refrigeration loop including: an evaporator in heat exchange relation to the outside surface of the heat transfer basin; a compressor; a condenser; and a refrigeration expansion control, all located within the cabinet. A separate product basin is configured to be removably received in the heat transfer basin. Spacers, in the form of short cylindrical stubs or buttons, are arranged in three groups spaced about the heat transfer basin and projecting into the heat transfer basin interior to maintain a prescribed space between the two basins. During use, that space contains a thermal transfer liquid, such as alcohol or glycol, serving as a thermal transfer medium between the two basins. A sterile drape, impervious to the thermal transfer medium, is disposed between the product basins exterior and the liquid thermal transfer media to preserve the sterile nature of the product basin. Surgically sterile liquid, such as sodium chloride solution, is placed in the product basin and congeals on the side of that basin when the refrigeration unit is activated. A scraping tool is utilized to remove congealed sterile material from the product basin side to thereby form a slush of desired consistency within the product basin. Some users of the system employ the scraping tool to chip the solid pieces from the basin side.
As noted in the above-referenced Templeton patent, the Keyes et al system has a number of disadvantages. In particular, the separate product basin must be removed and resterilized after each use. Additionally, the glycol or other thermal transfer medium is highly flammable or toxic and, in any event, complicates the procedure. The Templeton patent discloses a solution to these problems by constructing an entirely new apparatus whereby the product basin is eliminated in favor of a sterile drape impervious to the sterile surgical liquid, the drape being made to conform to the basin and directly receive the sterile liquid. Congealed liquid is scraped or chipped from the sides of the conformed drape receptacle to form the desired surgical slush. The Faries, Jr. et al patent U.S. Pat. No. (5,163,299) notes that scraping congealed liquid from the drape is undesirable in view of the potential for damage to the drape, resulting in a compromise of sterile conditions. In a solution to the problem, the patent proposes that the drape be lifted or otherwise manipulated by hand to break up the congealed liquid adhering to the drape. Although this hand manipulation is somewhat effective, it is not optimal, and often is inconvenient and constitutes an additional chore for operating room personnel.
The aforesaid Faries, Jr. et al patents (U.S. Pat. Nos. 5,502,980, 5,400,616 and 5,331,820) address the problem of removing the congealed liquid from the sides of the conformed drape receptacle in a surgical slush machine. Specifically, the drape is conformed to a cooled basin to establish a sterile field above the basin. The conformed drape receptacle collects a congealed sterile liquid (e.g. saline) in a sterile slush-like consistency. The congealed liquid tends to attach to sides of the drape receptacle in large clumps or pieces rather than automatically collecting within the drape receptacle interior. The Faries, Jr. et al patents U.S. Pat. No. (5,502,980, 5,400,616 and 5,331,820) disclose several techniques for automatically manipulating the drape relative to the basin wall to thereby cause the congealed liquid to detach from the drape receptacle sides and collect interiorly as desired slush. Some of the techniques include: reciprocating the bottom of the conformed drape receptacle up and down, disposing a plate on the drape for reciprocating the bottom of the conformed drape receptacle up and down, alternately twisting the bottom of the drape receptacle in opposite directions, lifting portions of the drape receptacle away from the basin wall by use of a wobble plate or disk, employing rollers to separate the drape receptacle from the basin wall, utilizing a hoop or ring disposed about the basin periphery to manipulate the drape receptacle, inflating and deflating a bladder situated between the basin and the lowermost portion or bottom of the drape receptacle, and pressurizing and aspirating the space between the sides of the drape receptacle and basin wall.
The present invention is an improvement in the configuration of drapes used as surgical slush receptacles, and in techniques for separating drape receptacle sides from the basin wall in order to dislodge congealed liquid from the drape. The surgical drapes, described in the Faries, Jr. et al patents as utilized in surgical slush machines to ensure sterility and dislodge congealed slush, although effective for their intended function, can stand some improvement. For example, there is no provision to secure these drapes to a surgical slush machine cabinet or housing; nor is there any indication on the drape as to which portion of the drape should be inserted into the basin. The result is an increased possibility of drape displacement and/or improper alignment of the drape on the housing. Moreover, the drapes do not have the capability of regulating the size of fragments of congealed liquid forming on the drape sides. Specifically, the smooth and continuous interior surface of the drape permits large and unusable fragments of congealed liquid to form and collect in the drape receptacle. These fragments require some intervention to be broken down into a slush consistency.
The technique disclosed in the above-referenced Faries et al patents for separating the conformed drape receptacle from the basin wall by the utilization of a bladder can also stand some improvement. Specifically, that bladder only has the capability of manipulating the drape at a single location, at a certain angle, and in a certain direction. Further, that bladder-driven drape has no provision for manipulation of substantial portions of the drape, thereby causing significant clumps of congealed liquid to remain on the unmanipulated drape portions.